The control of mold, mildew, algae, fungi and other microbes or microorganisms in bathrooms, shower stalls, and other moist or humid environments has long been a matter of concern. Biocides such as mildewcide, antimicrobial, antiseptic, disinfectant, sanitizer, germicide, algaecide, slimicide, antifouling agent, or preservative are typically employed to remove microbes from an area and prevent their recurrence. The use of biocides in the control or prevention of microbial growth requires effective contact between the biocide and the microbe. One problem in achieving effective and long lasting control of microbial growth has been the ease by which commercially available biocidal compositions can be washed from most substrates by the application of moderate volumes of water. In moist environments such as a home bathroom, for example, the surfaces of walls and floors around tubs, shower stalls, and sinks often experience daily exposure to significant volumes of water. This daily exposure to water washes conventional biocides from the surfaces to which they are applied, requiring frequent reapplication to retain a desired level of antimicrobial action. Consequently, some effort has been devoted to the search for a biocide containing material that will remain on a substrate for an extended period of time to make frequent reapplication unnecessary.
Different compositions have been proposed as effective in achieving the controlled release of biocides. Adherent controlled release microbiocides are described in the patent literature including the patents to Young et al., U.S. Pat. Nos. 4,500,337 and 4,500,339. These patents describe compositions containing microbiocide, hydrolyzable silanes or organopolysiloxanes, hydrolyzable organic titanium compounds and hydroxyl containing organopolysiloxanes or carbinol containing polymers. The Young et al. patents require that the polymers employed in the described compositions contain carbinol groups to promote cross-linking with the silanes in the composition. The compositions proposed by Young et al., however, are solvent based (e.g.. not water-based) formulations. Based on the disclosed chemistry, these compositions cannot be easily removed after being applied to a substrate. Consequently, they are not well suited for use by individuals in home bathroom environments, for example.
Other approaches include the use of a water soluble polymers such as polyester resin containing phenylindane dicarboxylic acid as well as polymeric compositions that contain a balance of hydrophilic monomers such as acrylates and modifying monomers such as cycloalkyl esters and aromatic esters. Other water-based coatings are known which may also contain a biocidal component. Known water-based coatings, however, have exhibited very poor adhesion to smooth non-porous substrates such as glass, ceramic tile, fiberglass and the like. In order to improve the adherence of such coatings, additional steps are normally taken in their application to substrates such as heat curing of the polymer or the prior application of an adhesion promoting primer to the substrate. Alternatively, it is known that the texture of the substrate surface can be partially abraded to create surface irregularities to which the polymer will more firmly adhere. In the absence of these additional measures, water-based compositions are easily removed from the substrate by warm water washing or even by exposure to conditions of high humidity.
In light of the above, the art has generally failed to provide effective water-based biocidal compositions which will readily from durable coatings when applied to smooth nonporous surfaces and which are capable of withstanding exposure to warm water rinsing for extended periods of time while releasing biocidal agents to the surrounding surface in a controlled manner. Hence, a substantial need exists for such water-based compositions for application onto smooth substrates such as tiled walls, for example. A need exists for such coatable compositions to form durable adherent coatings capable of remaining on the substrate without the use of adhesion promoting primers or other surface modifying treatments and which will slowly release biocide to the surrounding substrate. It is desirable to provide such coatable compositions capable of forming adherent but removable coatings (e.g., by alkaline washing) that will withstand substantial exposure to significant, and even continuous, warm water rinsing while remaining biocidally effective for an extended period of time.